ES2554352T3 - Wet curling process - Google Patents

Abstract

A method of wet curling absorbent paper base sheets, the method comprising the steps of: (a) forming an emerging web (118) comprising at least a significant proportion of recycled fibers, wherein at least a significant proportion of the recycled fibers, as determined on a length-weighted basis, exhibit flattened ribbon cellulosic fibers; (b) applying a crimping adhesive coating comprising a mixture of polyvinyl alcohol and a polyamide cross-linked with epichlorohydrin to a Yankee dryer (124); (c) passing the emerging web (118) through a contact line (126) defined between a suction pressure roller (128) and the Yankee dryer (124); and (d) adhering the emerging web (118) to the Yankee dryer (124) with a pressure that is controlled by controlling the load between the suction pressure roller (128) and the Yankee dryer (124); (e) drying the emerging web (118) over the Yankee dryer (124) to a moisture content that corresponds to a web sheet temperature (118) of between 110°C to 121°C; (f) controlling, during the drying step, the temperature of the sheet, immediately before a curling blade (60), at between 110 ° C and 121 ° C, the temperature of the sheet being measured just before the curling stage; (g) curling the emerging web (118), at a sheet temperature between 110ºC and 121ºC, from the Yankee dryer (124) with the curling blade (60) resting against the Yankee dryer (124) to form a wet band (118); and (h) continuing the crimping step, drying the wet web (118) to form a dry web.

Description

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4,675,394; 5,240,562; 5,138,002; 5,085,736; 4,981,557; 5,008,344; 4,603,176; 4,983,748; 4,866,151; 4,804,769 and

5,217,576. Modified starches sold under the trademarks COBOND®1000 and COBOND®1000 Plus, from the National Starch and Chemical Company of Bridgewater, N.J. Before use, the cationic aldehyde water soluble polymer can be prepared by preheating an aqueous suspension of approximately 5% solids, maintained at a temperature of approximately 116 ° C (240 ° F) and a pH of approximately 2.7 for approximately 3, 5 minutes. Finally, the suspension can be cooled and diluted by the addition of water to produce a mixture of approximately 1.0% solids at less than 54 ° C (130 ° F).

Other temporary wet strength agents, also available from the National Starch and Chemical Company, are sold under the trademarks CO-BOND® 1600 and CO-BOND® 2300. These starches are supplied as aqueous colloidal dispersions and do not require preheating before its use.

Temporary wet strength agents such as glyoxylated polyacrylamide can be used. Temporary wet strength agents such as glyoxylated polyacrylamide resins are produced by reacting acrylamide with diallyl dimethyl ammonium chloride (DADMAC) to produce a cationic polyacrylamide copolymer that is finally reacted with glyoxal to produce a cationic crosslinker resistance resin in temporary or semi-permanent wet, glyoxylated polyacrylamide. These materials are generally described in US Patent 3,556,932 of Coscia et al. and U.S. Pat. No. 3,556,933 to Williams et al. Resins of this type are commercially available under the trade name of PAREZ 631 NC, from Bayer Industries. Different molar ratios of acrylamide / DADMAC / glyoxal can be used to produce cross-linking resins, which are useful as wet strength agents. In addition, other dialdehydes can be substituted with glyoxal to produce wet strength characteristics.

Suitable dry strength agents include starch, guar gum, polyacrylamides, carboxymethyl cellulose and the like. Particularly useful is carboxymethyl cellulose, an example sold under the trade name Hercules CMC, of Hercules Incorporated of Wilmington, Del. According to one embodiment, the pulp may contain from 0 to 7.5 kg / ton (0 to 15 pounds / ton) of dry strength agent. According to another embodiment, the pulp may contain 0.5 to 2.5 kg / ton (1 to 5 pounds / ton) of dry strength agent.

Suitable solvents are also known to the skilled technician. The softeners or softeners can also be incorporated into the paste or sprayed on the web after forming. The present invention can also be used with softening materials that include, but are not limited to, the class of amide amide salts derived from partially acid neutralized amines. Such materials are described in US Patent 4,720,383. Evans, Chemistry and Industry, July 5, 1969, pp. 893-903; Egan, J. Am. Oil Chemist’s Soc., Vol. 55 (1978), pp. 118-121 and Trivedi et al., J. Am. Oil Chemist’s Soc., June 1981, pp. 754-756, indicate that softeners are often commercially available only as complex mixtures instead of individual compounds. Although the following discussion will focus on the predominant species, it should be understood that commercially available mixtures would generally be used in practice.

In many cases, a suitable softening material can be derived by alkylation of a condensation product of oleic acid and diethylenetriamine. Synthesis conditions that use a deficiency of alkylating agent (for example, diethyl sulfate) and only one alkylation step, followed by pH adjustment to protonate the non-ethylated species, result in a mixture consisting of cationic ethylated species and cationic non-ethylated. A smaller proportion (for example, about 10%) of the resulting amine amide cyclizes to imidazoline compounds. Since only the imidazoline portions of these materials are quaternary ammonium compounds, the compositions as a whole are pH sensitive. Therefore, in the practice of the present invention with this class of chemicals, the pH in the head box should be approximately 6 to 8, more preferably 6 to 7 and most preferably 6.5 to 7.

Quaternary ammonium compounds, such as dimethyl dialkyl quaternary ammonium salts are also suitable, in particular when the alkyl groups contain from 10 to 24 carbon atoms. These compounds have the advantage of being relatively insensitive to pH.

Biodegradable softeners can be used. Representative biodegradable cationic softeners / glides are described in US Patents 5,312,522; 5,415,737; 5,262,007; 5,264,082; Y

5,223,096. The compounds are biodegradable diesters of quaternary ammonium compounds, quaternary amines-esters and biodegradable vegetable oil based esters functional with quaternary ammonium chloride and dierucyldimethyl diester ammonium chloride which are representative biodegradable softeners.

In some embodiments, a particularly preferred sliding composition includes a quaternary amine component as well as a non-ionic surfactant.

In Figure 1, a band of biaxially undulating cellulosic fibers 88 is characterized by an intersection of curling bars 92 and undulations defining the roughness 90 on the air side thereof, the curling bars 92 that extend transversely in the transverse direction of the machine, the ridges 90 extending longitudinally in the direction of the machine, the band 88 having grooves 94 between the

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Table 2: Base sheet specifications

Base sheet

Unbleached Bleached

Base Weight (g / m2)

29 (28.0 - 30.0) 47.2 (45.6 - 48.8) 27 (26.0 - 28.0) 43.9 (42.3 - 45.6)

Caliber (mm / 8-layers)

67 (59 - 75) 1.7 (1.50 - 1.91) 67 (59 - 75) 1.70 (1.50 - 1.91)

MD Dry Traction (g / cm)

5500 (4300-6800) 722 (564-892) 5100 (3900 - 6400) 669 (512 - 840)

Dry Traction CD (g / cm)

3500 (2500 - 4500) 459 (328 - 591) 3150 (2150 - 4150) 413 (282 - 545)

MD / CD ratio

1.5 1.6

Wet Traction (g / cm)

950 (700 min.) 125 (92 950 (700 min.) 125 (92)

MD Stretch

8% (5% -10%) 8% (5% -10%)

WAR (seconds)

30 twenty

Raw material

100% recycled containing at least 40% of PCW 40% Light House SKF PCW 32% SW BCTMP 28% Peace River SWK

Curly Blade

Wave depth 0,762mm (12 tpi / 0,030 ”) Wave depth 0,762mm (12 tpi / 0,030 ”)

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Claims (1)

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